A fixed magnetic disk device has often been used in recent years as an external recording device for information processing devices including computers. FIG. 6 shows the magnetic recording disk (magnetic recording medium) generally used in this fixed magnetic disk device. The magnetic recording disk has a non-magnetic metal layer 12 formed on a non-magnetic substrate 11 which forms a non-magnetic base 1. A non-magnetic metal base layer 2 is laminated on the non-magnetic base 1 and a magnetic layer 3 is formed on the metal base layer 2. The magnetic layer 3 consists of a ferromagnetic alloy of cobalt-chrome-tantalum (Co-Cr-Ta) in thin film form. An amorphous carbon protective layer 4 if from on the magnetic layer 3. The magnetic recording disk also includes a lubrication layer 5 disposed on the protective layer 4.
The non-magnetic base 1 used in the device may include a glass substrate 11 that has been subjected to mirror grinding and formed with the non-magnetic metal layer 12 consisting of Cr, an anodized aluminum (such as ALUMITE) base substance or a ceramic base substrate. This non-magnetic base 1 may be polished and formed with irregularities using textures as required. The metal base layer 2 consists of Cr with a film thickness of 1000 .ANG.. The magnetic layer 3 is composed of Co.sub.86 Cr.sub.12 Ta.sub.2 with a film thickness of 500 .ANG.. The protective layer 4 includes amorphous carbon with a film thickness of 200 .ANG.. The layers are laminated in the above order using a sputtering process while heating the non-magnetic base substance to 320.degree. C. and applying a DC voltage of 200 V. Furthermore, a fluorocarbon-based liquid lubrication agent is coated on the protective layer 4 to form a lubrication layer 5 with a film thickness of 20 .ANG.. A magnetic recording disk thus manufactured exhibits good mechanical properties such as mechanical strength and dimensional accuracy, as well as good magnetic properties such as a coercive force Hc as good as about 1300 Oe and a Br.d which is a product of residual magnetic flux density and the magnetic layer film thickness as good as about 400G. .mu.m.
As a result of the increase in the amount of information available, as well as its increased diversity in recent years, the needs of large quantity processing of information have created a strong demand requiring that fixed magnetic disk devices have a higher recording density and a larger capacity. Accordingly, also in magnetic recording disks used in magnetic disk devices, a medium that can further reduce the flotation distance of the magnetic head is required to comply with the need for a higher recording density and a larger capacity. Generally, magnetic disk devices use a contact-start-stop (CSS) system to read and write information, wherein a magnetic head in operation floats slightly above a magnetic recording disk to read or write information. In this CSS system when the operation is stopped, the magnetic head contacts the magnetic recording disk surface. Therefore, if the magnetic recording disk surface has been mirror-polished, the magnetic head may get stuck on the magnetic recording disk surface because of the large coefficient of friction that exists between the magnetic head and the magnetic recording disk. In addition, a large frictional force generated from the magnetic head sliding on the magnetic recording surface upon actuation may cause the magnetic layer to become worn out. Therefore, although the magnetic recording disk with a construction as shown in FIG. 6 has superior surface smoothness making it possible to reduce the flotation distance of the magnetic head, it is also not so reliable as a magnetic recording disk because of the sliding characteristics of the magnetic head as described above. On the other hand, increasing the surface roughness on the magnetic recording disk reduces the coefficient of friction between the magnetic recording disk surface and the magnetic head, thereby making it possible to prevent the magnetic head from getting stuck on the magnetic recording disk, which improves the sliding characteristics of the magnetic head. However, increasing the surface roughness on the magnetic recording disk causes a problem in that it requires a larger flotation distance for the magnetic head to prevent a head crash, which in turn prevents any increase in the recording capacity.
In the light of these problems, it is the objective of the present invention to provide a magnetic recording medium and a method for the manufacture thereof that can improve the sliding characteristics of a magnetic recording disk while maintaining a small surface roughness and increasing the recording density and capacity by the reducing flotation distance for the magnetic head.